Abstract The National Coal Resource Assessment (NCRA) project of the U.S. Geological Survey (USGS) has assessed the quantity and quality of the nation's coal deposits that potentially could be mined during the next few decades. For eight years, geologic, geochemical, and resource information was collected and compiled for the five major coal-producing regions of the United States: the Appalachian Basin, Illinois Basin, Northern Rocky Mountains and Great Plains, Colorado Plateau, and the western part of the Gulf of Mexico Coastal Plain (Gulf Coast) region (Figure 1). In particular, the NCRA assessed resource estimates, compiled coal-quality information, and characterized environmentally sensitive trace elements, such as arsenic and mercury, that are mentioned in the 1990 Clean Air Act Amendments (U.S. Environmental Protection Agency, 1990). The results of the USGS coal assessment efforts may be found at: http://energy.cr.usgs.gov/coal/coal-assessments/index.html and a summary of the results from all assessment areas can be found in Ruppert et al. (2002) and Dennen (2009). Detailed assessments of the major coal-producing areas for the Gulf Coast region along with reviews of the stratigraphy, coal quality, resources, and coalbed methane potential of the Cretaceous, Paleocene, and Eocene coal deposits are presented in this report (Chapters 5-10).

Abstract The National Coal Resource Assessment (NCRA) team of the U.S. Geological Survey (USGS) has assessed the quantity and quality of coal beds and zones that could be mined during the next 20 years or more. Geologic, geochemical, and resource information was collected and compiled for the five major coal-producing regions of the United States: the Appalachian Basin, Illinois Basin, Northern Rocky Mountains and Great Plains, Colorado Plateau, and the Gulf of Mexico Coastal Plain, (Gulf Coast) (Figure 1). In particular, the NCRA assessed coal-quality information and characterized environmentally significant trace elements, such as arsenic and mercury, that are defined in and administered by 1990 Clean Air Act Amendments (U.S. Environmental Protection Agency, 1990). The results of various USGS coal assessment efforts may be found at: http://energy.cr.usgs.gov/coal/coal_assessments/index.html , and a summary of the results from all assessment areas can be found in Ruppert et al. (2002) and Dennen (2009). A more detailed assessment for the Gulf Coast region includes reviews of the coal geology, resource potential, and quality of coals in four areas (Figure 2A and other chapters of this volume). These areas selected for study (Figure 2A) are described in this report as: (1) the Sabine uplift in Louisiana

Abstract Selected areas of the Gulf of Mexico Coastal Plain have been assessed for coal resources by the U.S. Geological Survey (USGS) as part of the National Coal Resource Assessment (NCRA). The purposes of the NCRA are (1) to digitally assess original and remaining (unmined) resources (Wood et al., 1983) for selected coal beds and zones that might be used in the near future, (2) to create publicly available coal-related stratigraphic and geo-chemical databases available in a geographic information system (GIS) framework, and (3) to provide geologic and geochemical information for the primary coal resources that will supply a major part of the nation's energy needs during the next few decades. The basis for the NCRA is the National Coal Resources Data System (NCRDS), a comprehensive database that has been compiled for coal resources by the USGS in association with various state agencies. The NCRA was limited to five priority regions in the United States (Pierce, 2001), including the Gulf of Mexico Coastal Plain Priority Region (hereinafter referred to as the Gulf Coast Region) (Figure 1). For the Gulf Coast Region, selected coal producing areas of Texas and Louisiana have been formally assessed in a quantitative manner (coal resource assessment areas of Figure 1), while nonproducing coal areas and areas of minor or former production were assessed qualitatively. In addition to the primary assessment, each priority region was evaluated for the federal lands component of the total coal resource.

Abstract Five priority regions of the United States were studied as part of the U.S. Geological Survey's (USGS) National Coal Resource Assessment (NCRA). They include the Gulf Coastal Plain, the northern and central Appalachian Basin, the Illinois Basin, the Colorado Plateau, and the Northern Rocky Mountains and Great Plains regions (Figure 1). Emphasis for the assessment has been on those coal beds and zones that may be mined in the next few decades. The results of various USGS coal assessment efforts may be found at: http:/ /energy.cr .usgs.gov/coal/coal-assessments/index.html, and a summary of the results from all assessment areas can be found in Ruppert et al. (2002) and Dennen (2009). Coal deposits are extensive throughout the Gulf Coastal Plain of Texas and Louisiana along the margin of the Gulf of Mexico Basin. In 2008, Texas was the sixth largest coal producer in the United States with an annual production of 39 million short tons (Energy Information Administration, 2009). Texas production followed that of Wyoming (467.6 million short tons), West Virginia (157.6 million short tons), Kentucky (120 million short tons), Pennsylvania (63.4 million short tons [exclusive of anthracite production]), and Montana (44.8 million short tons). Most of the coal mined in the Gulf Coast is used for mine-mouth power plants, which generate about 20 percent of the electricity in Texas.

Abstract The Wilcox Group (Paleocene to Eocene) of the Sabine uplift, a structural arch in northeastern Texas and northwestern Louisiana (Figure 1), has lignite zones that approach subbituminous rank (see Chapter 4, this publication). These coals are among the highest quality resources known within the Gulf Coastal Plain because of their low ash yield and sulfur content. The surface expression of the Sabine uplift is defined by the contact between coal-bearing rocks of the Wilcox Group and overlying fluvial rocks of the Carrizo Sand, which is the basal unit of the Claiborne Group (Figures 2, 3). The Sabine uplift study area includes parts of Harrison, Marion, Nacogdoches, Panola, Rusk, Sabine, San Augustine, and Shelby Counties in Texas and Bossier, Caddo, De Soto, Natchitoches, Red River, and Sabine Parishes in Louisiana (Figure 1). Adjacent counties and parishes that include the subsurface Wilcox Group extend the regional Sabine uplift area. The Wilcox in the subsurface is underlain by the Midway Group (Figure 3), a mudstone-dominated marine sequence of Paleocene age. Quaternary alluvium and terrace deposits overlying the Wilcox Group at the surface are limited to areas of modern drainage. The total thickness of the Wilcox Group within the Sabine uplift area ranges from approximately 400 ft on outcrop to 2500 ft in subsurface (Kaiser, 1990). In a few places, the contact between the overlying Carrizo Sand and Wilcox Group is erosional, but in other places, the contact is gradational.

Abstract The lower part of the Wilcox Group of northwest Louisiana contains shallow (less than 500 ft) coal deposits that are mined for use in mine-mouth electric power-generating plants. The coal deposits, which are lignite A in apparent rank (Pierce et al., 2011), occur on the eastern part of the Sabine uplift (Figure 1). The coal zones and associated strata in the assessment area generally dip away from the axis of the Red River-Bull Bayou dome that is located in the north-central part of the Louisiana Sabine assessment area (Figure 1). This assessment area includes parts of four parishes: De Soto, Red River, Natchitoches, and Sabine (Figure 2). The assessment area was selected because of its proximity to current mining areas and the availability of stratigraphic data in the area. The assessment area is roughly 60 miles long and 15 miles wide and generally extends across the central-eastern part of the Sabine uplift in northwest Louisiana (Figure 2). More than 950 stratigraphic records from rotary and core drill holes were used to assess the coal resources of the Louisiana Sabine area. Of these, 210 are public data points and are located in or near the areas that have been permitted or proposed for surface mining (Figure 2; Appendix 1). Most of the stratigraphic data used for this assessment were provided to the U.S. Geological Survey (USGS) on a confidential basis by various coal companies for use in regional studies.

Abstract The surface exposure of the Paleocene Wilcox Group in northeast Texas varies in width from 9 to 27 mi along an arcuate outcrop that extends southwest approximately 156 mi from the Texas-Arkansas State line to 32° latitude. Parts of Bowie, Camp, Cass, Franklin, Henderson, Hopkins, Morris, Navarro, Rains, Titus, Van Zandt, and Wood Counties are included in this outcrop belt (Figure 1). This area forms the northwestern flank of the East Texas Basin (Figure 2), the axis of which separates northeast Texas from the Sabine uplift structural area. The Wilcox Group dips south and southeast at 2° or less toward the axis of the East Texas Basin, with the exception of local salt-dome structures and a transcurrent structural high that extends from Monticello to Martin Lake (Figure 1). The Wilcox Group conformably overlies the mudstone-dominated Midway Group, a marine unit of lower Paleocene age (Figure 3). In most of northeast Texas, the Wilcox is overlain and locally scoured by the Carrizo Sand of the Claiborne Group. Where the Car-rizo Sand is absent in extreme northeast Texas (Morris and Cass Counties, Figure 1), marine sandstone and mudstone deposits of the Reklaw Formation overlie the Wilcox Group (Figure 3). Holocene deposits overlie the Wilcox Group in areas of modern-day drainages. The thickness of the Wilcox Group in northeast Texas increases downdip from about 500 ft near the outcrop to approximately 2000 ft near the axis of the East Texas Basin

Abstract The Wilcox Group of northeast Texas contains shallow (less than 500 ft) coal deposits that are mined for use in mine-mouth electric power generating plants. The coal deposits, which are lignite in apparent rank ( Pierce et al., 2011 ), are separated from similar shallow coal deposits in the Sabine uplift area by the East Texas Basin (Figure 1 ). The coal zones and associated strata in the northeast assessment area generally dip to the south and southeast at 28 or less toward the axis of the East Texas Basin. The northeast Texas resource assessment area includes parts of nine counties (Figure 2 ). Abstract The Wilcox Group of northeast Texas contains shallow (less than 500 ft) coal deposits that are mined for use in mine-mouth electric power generating plants. The coal deposits, which are lignite in apparent rank (Pierce et al., 2011), are separated from similar shallow coal deposits in the Sabine uplift area by the East Texas Basin (Figure 1). The coal zones and associated strata in the northeast as-sessment area generally dip to the south and southeast at 2° or less toward the axis of the East Texas Basin. The northeast Texas resource assessment area includes parts of nine counties (Figure 2). This assessment area was selected because of its prox-imity to current mining areas and the availability of strat-igraphic data in the area. The northeast assessment area is roughly 60 mi long and 30 mi wide and generally fol-lowstheoutcropofthePaleocene-EoceneWilcoxGroup in northeast Texas (Figures 1, 2). More than 1500 stratigraphic records from rotary and core drill holes were used to assess the coal resources. Of the 1500 drill holes, 64 are public data points that are located in areas permitted for surface mining (Figure 2; appendix 1). Most of the stratigraphic data used for this assessment were provided to these U.S. Geological Survey (USGS) regional studies on a confidential basis by various coal companies.

Abstract Coal deposits in the Wilcox Group of central Texas have been regarded as the richest coal resources in the Gulf Coastal Plain. Although minable coal beds appear to be less numerous and generally higher in sulfur content (1 percent average, as-received basis; table 1 ) than Wilcox coal deposits in the Northeast Texas and Louisiana Sabine assessment areas (0.5 and 0.6 percent sulfur, respectively; table 1 ), net coal thickness in coal zones in central Texas is up to 32 ft thick and more persistent along strike (up to 15 mi) at or near the surface than coals of any other Gulf Coast assessment area. The rank of the coal beds in central Texas is generally lignite (table 1 ), but some coal ranks as great as subbituminousC have been reported (Mukhopadhyay, 1989). The outcrop of the Wilcox Group in central Texas strikesnortheast, extends for approximately 140 mi between the Trinity and Colorado Rivers, and covers parts of Bastrop, Falls, Freestone, Lee, Leon, Limestone, Milam, Navarro, Robertson, andWilliamson Counties (Figure 1 ). Three formations, in ascending order, the Hooper, Simsboro, and Calvert Bluff, are recognized in central Texas (Figure 2 ). The Wilcox Group is underlain conformably by the Midway Group, a mudstone-dominated marine sequence, and is overlain and scoured locally by the Carrizo Sand, a fluvial unit at the base of the Claiborne Group.

Abstract The Wilcox Group of central Texas contains shallow (less than 500 ft) coal deposits that are mined for use in mine-mouth electric power generating plants. These coal deposits range in apparent rank from lignite to sub-bituminous (Pierce et al., 2011) and are similar in rank and composition to shallow coal deposits in the northeast and south Texas areas (Figure 1). The coal zones and associated strata in the central Texas assessment area generally dip to the southeast toward the Gulf of Mexico coastline and basin center. The central Texas resource assessment area includes parts of eight counties (Figure 2). The assessment area was selected to encompass current mining areas and areas with available subsurface stratigraphic data. The assessment area is roughly 160 miles long and 5 to 25 miles wide and generally follows the outcrop of the Paleocene to Eocene Wilcox Group in central Texas (Figures 1, 2). Approximately 1800 subsurface stratigraphic records from rotary and core drill holes were used to assess the resources of the central Texas assessment area. Of the 1800 drill holes, only 167 are public data points and are primarily located in the areas that have been permitted for surface mining (Figure 2; Appendix 1). The remaining 1632 drill holes, which are distributed throughout the assessment area, were provided to the U.S. Geological Survey (USGS) on a confidential basis by various coal companies for use in regional studies.

Abstract Coal deposits of the undivided Wilcox Group and its southern equivalent Indio Formation (Paleogene) of south Texas are among the coal resources that are not evaluated quantitatively in the current Gulf Coastal Plain coal re-source assessment. South Texas Wilcox and Indio coals have not been extensively mined, nor have they been mined commercially for at least the past 60 years. These coals constitute only about 1 percent of the demonstrated coal resources within the Texas Gulf Coastal Province. In contrast to the Wilcox coal resources of the assessed areas of the Sabine uplift of Texas and Louisiana, and of northeast Texas and central Texas (see Warwick et al., 2011a, b, c), Wilcox and Indio coal beds of south Texas are few in number, each generally less than 5 ft thick, and highly discontinuous. Furthermore, analytical data indicate that the sulfur content and ash yields of south Texas Wilcox and Indio coals generally exceed those of other Texas coals. Although these and other factors preclude the likely development of Wilcox or Indio coal resources in the near future, the comparatively elevated rank of these deposits has attracted recent interests related to coalbed methane production (SanFilipo, 1999; Warwick et al., 2002a, 2007b). The south Texas coal area is defined by the Colorado River to the northeast and the Rio Grande to the southwest and occurs within the Rio Grande Embayment (Figure 1). The youngest Tertiary coal-bearing rocks of this region occur sporadically

Abstract Near the Barents Sea coast in northern Timan, turbidites of probable Neoproterozoic age are intruded by pre-tectonic dolerites and a major suite of gabbros, granites and syenites (some nepheline bearing). Zircon ion microprobe dating of three plutons has yielded well-defined ages of 613–617 Ma. This alkaline igneous activity apparently represents a final phase of Vendian extensional magmatism prior to Timanian Orogeny. Previous work on late to post-orogenic calc-alkaline granites in the basement beneath the Pechora Basin, three hundred kilometres towards the SE, has yielded c. 550–560 Ma single zircon Pb-evaporation ages. These compositionally different intrusive suites are inferred to constrain the main phase of Timanian Orogeny to c. 610–560 Ma.

Abstract Near the Barents Sea coast in northern Timan, turbidites of probable Neoproterozoic age are intruded by pre-tectonic dolerites and a major suite of gabbros, granites and syenites (some nepheline bearing). Zircon ion microprobe dating of three plutons has yielded well-defined ages of 613–617 Ma. This alkaline igneous activity apparently represents a final phase of Vendian extensional magmatism prior to Timanian Orogeny. Previous work on late to post-orogenic calc-alkaline granites in the basement beneath the Pechora Basin, three hundred kilometres towards the SE, has yielded c. 550–560 Ma single zircon Pb-evaporation ages. These compositionally different intrusive suites are inferred to constrain the main phase of Timanian Orogeny to c. 610–560 Ma.

Abstract The lignite deposits within the upper Eocene Yegua Formation (Claiborne Group) and the overlying Jackson Group are among the coal resources that were not quantitatively assessed as part of the U.S. Geological Survey's (USGS) National Coal Resource Assessment (NCRA) program in the Gulf Coastal Plain coal province. In the past, these lignite-bearing stratigraphic units often have been evaluated together because of their geographic and stratigraphic proximity (Fisher, 1963; Kaiser, 1974; Kaiser et al., 1980; Jackson and Garner, 1982; Kaiser, 1996) (Figures 1, 2). The term “Yegua-Jackson trend“ is used informally herein for the lignite-bearing outcrops of these Late Eocene deposits in Texas. Lignite beds in the Yegua-Jackson trend generally are higher both in ash yield and sulfur content than those of the underlying Wilcox Group (Figure 2 ). Recent studies (Senkayi et al., 1987; Ruppert et al., 1994; Warwick et al., 1996, 1997) have shown that some lignite beds within the Yegua-Jackson trend contain partings of volcanic ash and host elevated levels of trace elements that have been identified as potentially hazardous air pollutants (HAPs) in the United States Clean Air Amendments of 1990. Lignite beds within the Yegua Formation are thin (less than or equal to 6 ft) and laterally discontinuous in comparison with most Wilcox Group deposits (Ayers, 1989a); in contrast, the Jackson Group lignite beds range up to 12 ft in total thickness and are relatively continuous laterally, extending nearly 32 mi along strike.

Abstract This review of lignites in Mississippi is a product of the U.S. Geological Survey (USGS) National Coal Resource Assessment (NCRA) of the Gulf Coast region (see Ruppert et al., 2002 ; Dennen, 2009 ; and other chapters of this publication). As a part of the NCRA, this project assessed the quantity and quality of coals in the Gulf Coastal Plain region. The primary stratigraphic interval of study is the Wilcox Group (Paleocene to Eocene) and selected coal-producing intervals (such as the Eocene Jackson and Claiborne Groups, and the Cretaceous Olmos Formation in south Texas) that are producing or have potential for producing coal in the near future.

Abstract This review of Alabama lignite deposits is a part of the U.S. Geological Survey (USGS) National Coal Resource Assessment (NCRA) of the Gulf Coast region (see Ruppert et al., 2002 ; Dennen, 2009; and other chapters of this publication). Because lignite is not currently mined in Alabama, a detailed assessment of the state was not made, and only a review is presented in this chapter.

Abstract This review of the lignite resources of Arkansas is a part of the U.S. Geological Survey's (USGS) National Coal Resource Assessment (NCRA) of the Gulf Coastal Plain Coal Province, which also includes coal-bearing areas in the states of Texas, Louisiana, Alabama, Mississippi, Tennessee, and Kentucky (see Ruppert et al., 2002 ; Dennen, 2009 ; and other chapters of this publication). Lignite mining is not planned in Arkansas in the immediate future, and the lignite resources of the state were not assessed in detail as part of the NCRA. This chapter includes reviews of the geology of the lignite-bearing units, historical mining, previous investigations of lignite resources, and coal quality. Palynological data for lignite samples collected in Arkansas as part of this work are presented in Table 1 .

Abstract This review of the lignite deposits of western Tennessee and the Jackson Purchase area in western Kentucky (Figure 1 ) is an updated report on part of the U.S. Geological Survey's National Coal Resource Assessment of the Gulf Coastal Plain Coal Province (see Ruppert et al., 2002 ; Hackley et al., 2006 ; Dennen, 2009 ; and other chapters of this publication). Lignite deposits of western Kentucky and Tennessee are an extension of the Gulf Coastal Plain Coal Province ( Cushing et al., 1964 ), and currently are not economic to mine. These deposits have not been extensively investigated or developed as an energy resource. This review includes a description of the geology of the lignite-bearing units, a discussion of the available coal quality data, and information on organic petrology. Palynological data for lignite samples collected in Kentucky and Tennessee as part of this work are presented in Table 1 . Lignite trace element data originally presented in Hackley et al. (2006) are not included in this report due to potential laboratory quality control issues during the time the samples were analyzed (U.S. Geological Survey Energy Resources Program, 2010).

Abstract This review of the lignite deposits of western Tennessee and the Jackson Purchase area in western Kentucky (Figure 1) is an updated report on part of the U.S. Geological Survey's National Coal Resource Assessment of the Gulf Coastal Plain Coal Province (see Ruppert et al., 2002 ; Hackley et al., 2006 ; Dennen, 2009 ; and other chapters of this publication). Lignite deposits of western Kentucky and Tennessee are an extension of the Gulf Coastal Plain Coal Province ( Cushing et al., 1964 ), and currently are not economic to mine. These deposits have not been extensively investigated or developed as an energy resource. This review includes a description of the geology of the lignite-bearing units, a discussion of the available coal quality data, and information on organic petrology. Palynological data for lignite samples collected in Kentucky and Tennessee as part of this work are presented in Table 1. Lignite trace element data originally presented in Hackley et al. (2006) are not included in this report due to potential laboratory quality control issues during the time the samples were analyzed ( U.S. Geological Survey Energy Resources Program, 2010 ).